🚀 go-pugleaf

In article <1993Jan20 221737 C16B9F.ADx@boi.hp.com> jmcvey@boi.hp.com  writes:

>I just called MEADE and talked with them about my 8" SCT.  Here
>are a few things I learned.  I welcome comments as to the validity
>of these things:

>1) It may take two hours for an SCT to reach thermal equilibrium.

Probably. What works for me is to set up outdoors in late afternoon, and
let the scope cool down with the day. I don't do anything critical
(like photography) until later in the night.

>2) You can do critical alignment by keeping the star in focus and
>   centering the airy disk within the diffraction ring pattern.

Do you mean alignment of the secondary mirror? And do you mean DEfocused?
If so, yes. In fact, that's the procedure listed in the Meade LX200 manual.

>3) A mask for the objective with two 2.5" holes on opposite sides
>   of the secondary will help achieve critical focus and will
>   demonstrate spherical aberation if you can't ever get the two
>   images to merge.

Yep, it works. There is a commercial product called, I think, Kwik-Focus,
which is advertised in _S&T_ and _Astronomy_ (*with* a photo of it, which
can be used as a guide to making your own ;-) ), but it's easier and cheaper
to make your own. I made one out of cardboard, and I stick it on with a wad 
of gaffer's tape on the secondary mirror cap. You could also make one out of 
a spare lens cap. Works just fine, though you need to use it on a fairly 
bright star, since it cuts out a lot of light. 
Also makes an adequate neutral density filter if you're observing a really 
bright Moon.



-- 
              Dave Palmer             dpalmer@csulb.edu

********************I finally found the perfect woman,*********************** 
*****************but she was looking for the perfect man*********************